Fixes autodiscovery of tables. 
Allows the FRM to be extracted from the ARZ file via archive_reader. 


storage/archive/archive_reader.c:
  Extract FRM command added.
  We now print the embedded comment
storage/archive/archive_test.c:
  Additional tests for FRM annd comment
storage/archive/azio.c:
  Filled in functionality for comment and frm.
storage/archive/azlib.h:
  Refactored position.
storage/archive/ha_archive.cc:
  Discovery mechanism filled in.